R help - Feb 2010 - Y average in plot

Hello All:

Can somebody please tell me how I can have the average of 'y' on the
graph
for different values of 'x in the following code?

ofn <- "xy.png"

bitmap(ofn, type = "png256", width = 21, height = 30, pointsize = 30,
bg "white",res=50)

ifn  <-  sprintf("xy.txt")

data <-  read.table(ifn)

names(data) <- c("x","y")

Graph <- plot(data$x, data$y)

dev.off()

Thanks,
MJK

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